I see intermixing of the terms quantum computer and quantum system. These are different concepts, and I think that's the source of the confusion. A quantum computer is a well defined thing. It's just like a classical computer but instead of just binary bits, it can work with qubits that support superposition. But it still needs programs just like a classical computer, and the results that we can actually read are binary in both cases.

Both of them are quantum "systems", in that both require quantum physics to work, if we're considering modern CPU gate sizes. Just, classical computers expose binary bits, and quantum computers expose qubits.

What I think you're picturing is a quantum "system", like a blob of quantum goo, that you can toss some "state" into and...something. But, that's not what a quantum computer is, any more than a classical computer is something you could throw into a blob of electrical goop and expect it to do anything.